Page 1340 - Clinical Small Animal Internal Medicine

1278 Section 11 Oncologic Disease

helpful to determine the extent of tumors and can also Prognosis
VetBooks.ir be used to obtain histopathologic samples. Computed Benign tumors of the larynx and trachea have a good
tomography (CT) and magnetic resonance imaging
prognosis when treated with surgical resection alone.
(MRI) provide three‐dimensional localization of the
tumor as well as its proximity to other vital structures Long‐term survival is also expected with treatment of
extramedullary plasmacytomas and granular cell tumors.
within the cervical region. This detailed imaging may Unfortunately, information is too limited to provide spe­
facilitate a diagnosis but is often required for treatment cific prognosis’ for dogs with other malignancies of the
planning. airway.
Laryngeal/tracheal lymphoma should be considered
Similar to dogs, little information is available regarding
part of a systemic disease process, therefore warranting the prognosis for cats. In one reported study, the median
complete staging as part of a diagnostic plan.
survival time for 27 cats with a variety of laryngeal and
tracheal tumors was only five days, with only 7% of
Therapy patients alive 12 months after diagnosis.
There is limited information regarding the treatment
of laryngeal tumors in dogs and cats. In dogs, benign
tumors of the larynx such as a rhabdomyoma or cyst Cancer of the Lung
can be removed surgically. Some cases require place­
ment of a temporary tracheostomy tube. Smaller benign Etiology/Pathophysiology
masses can be removed via a transoral approach or Primary lung tumors are rare in dogs and cats compared
through a ventral laryngotomy. Postoperative inflam­ to humans. The most common primary lung tumor in
mation and obstruction may necessitate temporary dogs is bronchoalveolar carcinoma, followed by adeno­
tracheostomy. For larger and/or more invasive tumors, carcinoma, adenosquamous carcinoma, and squamous
a partial or complete laryngectomy with a permanent cell carcinoma. Other primary lung tumors include his­
tracheostomy can be considered. Permanent tracheos­ tiocytic sarcoma, neuroendocrine tumors, and primary
tomy, providing relief of upper airway obstruction, is a pulmonary sarcomas. Benign primary lung tumors
form of treatment for humans but has limited use in include adenomas and fibromas. The most common pri­
veterinary medicine. mary lung tumor in cats is adenocarcinoma, followed by
Reported complications of complete laryngectomy bronchoalveolar carcinoma, squamous cell carcinoma,
in dogs include stomal collapse, the formation of a and adenosquamous carcinoma.
tracheoesophageal fistula, pharyngeal dehiscence, In both cats and dogs, primary lung tumors can spread
and ablation of the parathyroid glands. Permanent via hematogenous or lymphatic routes. This may occur
tracheostomy in cats carries a 67% complication rate regionally, to intrathoracic lymph nodes, other lung
with 29% in‐hospital mortality. A temporary gastrostomy lobes, and the pleura, or distantly throughout the body.
tube should be considered for any patient undergoing More than three‐quarters of cats with pulmonary tumors
aggressive laryngotomy. will develop metastasis. Local invasion of tumors within
Radiation therapy is used for treating invasive or nonre­ the adjacent pulmonary parenchyma can occur.
sectable tumors and is effective for treating lymphomas In some cases, it is difficult to determine if a pulmonary
and plasma cell tumors. However, limited evidence‐ tumor represents a primary cancer versus a metastatic
based information exists. Chemotherapy, with or with­ lesion from a distant site. Immunohistochemical stains
out surgery, may also be effective. can be helpful in such cases, as can complete and thor­
Tumors of the trachea should be treated with surgery, ough staging to evaluate for disease at distant sites.
which is curative for benign osteochondral tumors.
Experimental evidence indicates that up to 50% of the Epidemiology
length of the trachea can be removed with successful
closure. Tension on the site of anastomosis is the limiting The relationship between environmental carcinogens
factor. Intraluminal stenting or bronchoscopic debulking and the development of lung tumors in dogs has been
can be palliative measures for relieving obstruction. As studied. One study showed that 75% of dogs with primary
with laryngeal tumors, the efficacy of radiation and/or lung tumors live in urban environments, but the results of
chemotherapy for non­hematologic tumors remains two other studies did not support this finding. The risk of
unproven but can be considered when surgery is not exposure to second‐hand smoke and development of lung
feasible. cancer in dogs has also been evaluated with conflicting